Carbon nanotube composite, method for making the same, and electrochemical capacitor using the same

Abstract

An electrochemical capacitor includes a first electrode, a second electrode, a membrane, and an electrolyte. The first electrode includes a carbon nanotube composite. The carbon nanotube composite includes a free-standing carbon nanotube structure, and a plurality of nano grains located on the carbon nanotube structure. The membrane is located between the first electrode and the second electrode, to separate the first electrode from the second electrode. The first electrode, the second electrode, and the membrane are disposed in the electrolyte.

What is claimed is: 
     
       1. An electrochemical capacitor comprising:
 a first electrochemical capacitor electrode comprising a carbon nanotube composite comprising a free-standing carbon nanotube structure and a plurality of nano grains located on the free-standing carbon nanotube structure; 
 a second electrochemical capacitor electrode; 
 a membrane located between the first electrode and the second electrode, to separate the first electrode from the second electrode; and 
 an electrolyte, 
 wherein the first electrochemical capacitor electrode, the second electrochemical capacitor electrode, and the membrane are disposed in the electrolyte. 
 
     
     
       2. The electrochemical capacitor of  claim 1 , wherein the free-standing carbon nanotube structure comprises a plurality of carbon nanotubes, the plurality of nano grains being located on the plurality of carbon nanotubes. 
     
     
       3. The electrochemical capacitor of  claim 2 , wherein the plurality of carbon nanotubes define a plurality of clearances in the free-standing carbon nanotube structure. 
     
     
       4. The electrochemical capacitor of  claim 1 , wherein the plurality of nano grains are selected from the group consisting of metal oxide grains, metal grains, and combinations thereof. 
     
     
       5. The electrochemical capacitor of  claim 4 , wherein a material of the metal oxide grains is selected from the group consisting of manganese dioxide, cobalt oxide, nickel oxide, ruthenium oxide, iridium oxide, and combinations thereof. 
     
     
       6. The electrochemical capacitor of  claim 4 , wherein a material of the metal grains is selected from the group consisting of copper, nickel, gold, silver, palladium, ruthenium, platinum, rhodium, and combinations thereof. 
     
     
       7. The electrochemical capacitor of  claim 1 , wherein the free-standing carbon nanotube structure comprises at least one carbon nanotube film. 
     
     
       8. The electrochemical capacitor of  claim 7 , wherein the at least one carbon nanotube film comprises a plurality carbon nanotubes entangled with each other. 
     
     
       9. The electrochemical capacitor of  claim 7 , wherein the at least one carbon nanotube film comprises a pressed carbon nanotube array. 
     
     
       10. The electrochemical capacitor of  claim 7 , wherein the at least one carbon nanotube film comprises a plurality of successively oriented carbon nanotube segments joined end-to-end by van der Waals attractive force therebetween. 
     
     
       11. The electrochemical capacitor of  claim 7 , wherein the at least one carbon nanotube film comprises a plurality of carbon nanotube films stacked with each other. 
     
     
       12. The electrochemical capacitor of  claim 1 , wherein the free-standing carbon nanotube structure comprises at least one carbon nanotube wire structure. 
     
     
       13. The electrochemical capacitor of  claim 1 , wherein the second electrochemical capacitor electrode comprises a carbon nanotube composite the same as that of the first electrode. 
     
     
       14. An electrochemical capacitor comprising:
 a first electrochemical capacitor electrode; 
 a second electrochemical capacitor electrode; 
 a membrane located between the first electrochemical capacitor electrode and the second electrochemical capacitor electrode, to separate the first electrochemical capacitor electrode from the second electrochemical capacitor electrode; and 
 an electrolyte to soak the first electrochemical capacitor electrode, the second electrochemical capacitor electrode, and the membrane; 
 wherein the first electrochemical capacitor electrode is a carbon nanotube composite film comprising at least one carbon nanotube film, and a plurality of nano grains, the at least one carbon nanotube film is also a current collector, the plurality of nano grains being located on and in contact with the plurality of carbon nanotubes. 
 
     
     
       15. The electrochemical capacitor of  claim 14 , wherein the plurality of nano grains is MnO 2  grains, NiO grains, or Co 3 O 4  grains. 
     
     
       16. The electrochemical capacitor of  claim 14 , wherein the at least one carbon nanotube film is a free-standing film comprising a plurality of carbon nanotubes joined end to end by van der Waals attractive force therebetween. 
     
     
       17. An electrochemical capacitor comprising:
 a carbon nanotube composite, used as a first electrochemical capacitor electrode and a current collector, comprising a free-standing carbon nanotube structure and a plurality of nano grains located on the free-standing carbon nanotube structure, the plurality of nano grains is MnO 2  grains, NiO grains, or Co 3 O 4  grains; 
 a second electrochemical capacitor electrode; 
 a membrane located between the carbon nanotube composite and the second electrochemical capacitor electrode, to separate the carbon nanotube composite from the second electrochemical capacitor electrode; and 
 an electrolyte, 
 wherein the carbon nanotube composite, the second electrochemical capacitor electrode, and the membrane are disposed in the electrolyte.